1. Field of the Invention
This invention relates to the management of gases released from a heat exchanger and, more particularly, to an apparatus and method for purging such gases that may be released.
2. Description of Related Art
In a heat exchanger, thermal energy is transferred from a first flow of hot fluid to a second flow of cooler fluid. For example, in one typical air-cooled heat exchanger used to cool a hot gas, the flow of the hot gas is directed through a number of parallel tubes. At a first header at a first end of the heat exchanger, each of a first plurality of the tubes defines an inlet, and each of a second plurality of the tubes defines an outlet. At the opposite end of the heat exchanger, the tubes are joined, e.g., by a second, or return, header. The return header can be a device that collects the gas flowing through the first plurality of tubes, with some mixing of the gas at the second end, and directs the gas through the second plurality of tubes. The hot gas flows in a generally U-shaped path through the tubes, i.e., the gas enters the inlet of a first tube at the first header, flows linearly through the entire length of the first tube, reverses direction at the return header, and then flows linearly through a second tube and out through the outlet at the first header. The tubes can be enclosed in a housing, such as a tubesheet or shell, through which a cool gas, such as air, can flow, typically in a direction that is transverse to the direction of the tubes. Thermal energy is transferred between the gases, e.g., from a hot gas flowing through the tubes to the cool air flowing through the housing.
Each tube can be a generally linear component that is formed separately, and the headers can provide a connection to the ends of the tubes. Each header can provide access ports so that the tubes can be accessed without disassembly of the entire heat exchanger. For example, each header can define a number of small holes, each being aligned with the end of a respective tube so that tube can be accessed through its respective hole in the header, e.g., to check or repair the tubes. The holes can be threaded, and a corresponding threaded plug can be secured in each hole to seal the hole during operation so that gas in the header is contained.
It may undesirable for the fluid passing through the tubes to leak or otherwise be released therefrom to the environment, and/or it may be undesirable for the fluid to exist in concentrated form outside the heat exchanger. For example, in the case of a flammable fluid such as hydrogen, it may be desirable to either contain the fluid entirely within the heat exchanger or, in the event of a small leak, to prevent the leaked fluid from collecting in concentrated form outside the heat exchanger. The possibility of such leaks can be reduced by alternate designs. For example, the plugs can be eliminated altogether or welded in place. However, such techniques generally make maintenance and inspection more difficult.
Thus, there exists a continued need for an improved apparatus and method for managing the possibility of such leaks from heat exchangers. The apparatus and method should be compatible with heat exchangers that have exposed headers or other components that present increased risk of leakage.